Abstract

Studies of inositol lipid-specific phospholipase C (PLC) have elucidated the main regulatory pathways for PLCβ and PLCγ but the regulation of PLCΔ isoenzymes still remains obscure. Here we demonstrate that an increase in Ca2+ ion concentration within the physiological range (0.1-10 μM) is sufficient to stimulate PLCΔ1, but not PLCγ1 and PLCβ1, to hydrolyse cellular inositol lipids present in permeabilized cells. The activity of PLCΔ1 is further enhanced in the presence of phosphatidylinositol transfer protein (PI-TP). Both full activation by Ca2+ ions and stimulation in the presence of PI-TP require an intact PH domain involved in the membrane attachment of PLCδ1. The physiological implication of this study is that PLCΔ1 could correspond to a previously uncharacterized PLC responsible for Ca2+ ion-stimulated inositol lipid hydrolysis observed in many cellular systems.